14 Pro Max screen locks up during calls

Hi andrewcweaver, We appreciate you reaching out to us. We understand that your device's screen freezes when making and receiving calls.

We’d like to gather additional details that may help us be in a better position to assist you. Are you experiencing this issue when making and receiving cellular calls, FaceTime calls, or both?

First, let’s check for a software update and make sure that you are running the latest version of iOS.

While it isn't inherently assured that an update will resolve the issue, updating to the latest software version for your device can help isolate potential software issues. 

Kindly secure a backup and update.

How to back up your iPhone, iPad, and iPod touch

Update your iPhone, iPad, or iPod touch

Then, check if you have to install a new carrier update.

The article below may help.

Manually update your carrier settings on your iPhone or iPad

Are you using a screen protector or a case that may interfere with your device's sensors?

If yes, please check if the issue persists if you remove your screen protector or your case.

Also, do you have any accessory that is connected or paired with your device?

If yes, please check if the issue persists if you disconnect or unpair your accessory.

Please keep us posted.

Take care!